libiptc is the library that is used to communicate
with netfilter, the internal kernel code in charge of firewalling and packet
filtering. This code and iptables were written by Paul
"Rusty" Russell. iptables was developed
using libiptc calls to get the job done.

If you want to have more information about iptables,
libiptc and the firewalling code, have a look at
links at the end of this document.